Motor-control system.



P. H. THOMAS. MOTOR CONTROL SYSTEM. APPLIOATION FILED no.4, 1903. RENEWED IAY 17, 1906.

7 945,006. Patented Dec. 28, 1909.

iii??? 0 0%? 2 um'rnn STATES PATENT OFFICE.

PERCY H. THOMAS; OF PITTSBURG, PENNSYLVANIA, ASSIGNOR T0 COOPER HEWITT ELECTRIC COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

MOTOR-CONTROL SYSTEM.

Patented Dec. 28, 1909.

Original application illed September 4, 1903, Seriai No. 171,882. Divided and this application filed Decemher 4, 1903, Serial No. 183,697. Renewed May 17, 1906. Serial No. 317,267.

To all whom it may concern:

Be it known that I, PERCY H. THOMAS, a citizen of the United States, and resident of Iittsburg, county of Allegheny, State of Pennsylvania, have invented certain new and useful Improvements in Motor-Control Systems, of which the following is a specification.

The object of this invention is to provide economical and simple means for gradually accelerating a direct current motor which is supplied with power from an alternating current source. As is well known, it is pos sible to obtain, gradual acceleration in such motors by the use of groups or steps of series resistances. This method is, however, uneconomical and requires resistances of considerable bulk. When this mode of acceleration is employed, the energy consumed by the resistances represents a cuttin down of the total energyof the circuit an consequently stands for a practical waste of energy inasmuch as the resistances contribute nothing to the active operation of the system. Under the operation of the invention disclosed herein, this waste is avoided. Practically the total energy of the circuit at any given time is-applied to the operation of the motor, and the desired acceleration of the motor is accomplished by applying to it successively larger and larger amounts of electrical energy, none of which is wasted.

In carrying out my inventions, I make use, among other things, of a so-called vapor converter adapted totransform alternating into direct currents. Incidentally the vapor converter employed may be provided with one or more additional or supplementary positive electrodes. I supply to the motor a gradually varying direct current potential from an alternating source, preferably from intermediate points of a transformer, the arrangement being such that during successive periods of operation successively higher and higher potentials are applied to the motor through the action of a suitable switch.

I have illustrated my invention in the accompanying drawings, in which- K Figures 1 and 2 are diagrams of circuits and apparatus adapted to carry out my invention. J In the drawings, 1 is the primary of a suitable transformer supplied from an alternating current source. The secondary of the transformer is shown at 2 as having taps 3, 4, 5,6 and 7 connected, respectively, to switch terminals 8, 9, 10, 11 and 12. From one extremity of the'transformer a wire 13 leads to one side of the work circuit including a direct current motor 14. The other side, 15, of the Work circuit is connected to the negative electrodes, 16, of a vapor converter, 17, the said converter be ing provided with two positive electrodes, 18 and 19. The electrode 18 is connected by a conductor, 20, with a switch terminal, 21,

and the electrode 19 is connected by a conductor, 22, with a switch terminal, 23.

The terminals 21 and 23 are adapted to cooperate with the described terminals 8, f), 10, 11 and 12, any suitable device being provided whereby relative movement between these sets of terminals can be obtained. It should, however, be stated that the terminal devices referred to are so proportioned that during their relative movement the terminal 23, for example, will make contact with the terminal 11 before the terminal 21 leaves-the terminal 12, and also that the terminal 21 will make contact with the terminal 1] betore the terminal" 23 leaves the same. This same relation holds with respect: to the members of any successive pair in the group of terminals 8, 9, 10, 11, and 12.

Across the terminals of the main transformer a circuit, 24, is placed, the same including the primary, 25,0:t a transformer, the secondary, 26, of which is connected to auxiliary positive electrodes, 27 and 28, inside the vapor converter 17. At an intermediate pomt in the secondary 26 a con ductor, 29, leads to the negative electrode 16 of the converter. In the conductor 29 I may include a choke coil, 30, the function of which is to store electrical energy during a rise of potential in the circuit and to discharge a portion of the stored energy during a fall of potential, whereby the negative electrode 16 is maintained at all times in an operative condition. This action is now Well understood, having been made the sub ject of several applications of myself and others in the United States Patent Office.

The. operation of the system thus far described 1s as follows: The direct "current motor 14 is started from rest by so operating the switch terminals 21 and 23 that the terminals 23 make contact with the terminal tap 'ot the motor or to supply it with energy 12, which is the lowestvoltage tap provided I from the secondary 2 of the main transformer. This ap lies the alternations from this. transformer 111 a given direction to the motor 14, these accumulations of electrical epergy being sup lied at the lowest voltage attainable from tie a paratus. To accelerate the motor, the switch terminals 21 and 23 are moved upward, the terminal 21 making contact with the terminal 12 before the terminal 23 leaves the terminal 12, thus running both positive electrodes 18 and 19 in parallel upon the tap 7. As the switch terminals move farther, the terminal 23 leaves the tap 7 leaving the terminal 18 to carry the current. A moment later, the terminal 23 makes contact with the terminal 11 of the tap 6, which is the tap on the next higher voltage, when the positive electrode 15) immediately supplies current to the direct current motor 11 at the voltage of the ti. The positive electrode 18, though still connected to the tap 7, no lon er su plies current to the motor 14, since the ten ency is for current to flow from the electrode 19 to the electrode 18. No current actually flows, however, into the electrode 18 in View of the initial reluctance characteristic of an electrode which tends to act as a. negative. As the switch terminals advance, the terminal 21 leaves the. terminal 12 and makes contact with the terminal 11 before the terminal 23 leaves the terminal 11, the two electrodes 18 and 15) thus acting in parallel to supply current. to the motor 14. The cycle of operations just described are then repeated between the taps (S and 5, 5 and 1, and so on until finally the desired acceleration is attained in the motor and the latter is efi'ected, it the conditions re quire, by the terminal voltage of the transformer. If it is desired to lessen the speed in lesser amount, the switch elements may be made to traverse the movements described in the reverse direction in which all the intermediate points of voltage will be applied to the motor also in a reverse direction. It must be noted, however, that in this case, since the positive electrode within the vapor converter which has the higher potential tends to supply current, it will be necessary for the switch terminal 23 to break the circuit every time it leaves a tap terminal. However, since the terminal 18 is always ready to supply the energy to the motor at a slightly lower potential, :1. comparatively simple circuit breaking device will suffice on the switch terminal 23. I am aware that a similar result has been obtained in some cases by the use of a sliding contact passing from tap to tap and broad enough to bridge two successive taps. Such a switching device is provided with an impedance coil to reduce the current which necessarily results from the short circuiting of a portion of the secondary ot the supply traiistormer. In the device described in Fig. 1, one contact bridges two taps from the transformer and no short circuit current. can flow, since neither positive electrode 18 or 15) can act. as a negative.

in case the motor gradual decrease in speed is required, it is desirable when the motor, running upon the maximum voltage, is to be. stopped to open the supply circuit by any suitable circuit. breaker, or where the character of the vapor device is suitable, by opening the circuit of the'auxiliary transformer 25, 26 at any suitable point.

The organization illustrated in Fig. 1 is adapted to supply to the motor, current of one direction, by utilizing every other alternation of the supply circuit. in Fig. 2, however, the corresponding motor is ati'cctcd by current of one direction in which both phases of the supply current are utilized. In this second figure of the drawing, the vapor converter is supplied with three main positive electrodes, E31. 32 and 3?). connected respectively to contact terminals 3t, 35 and 36. The said terminals are adapted to cooperate with other switch terminals having a relative movement as regards the first named terminals, the group otcooperating terminals being shown at 37, 38, 3t), 40, 41. and 42. Each of these terminals is connected by a tap with a loop of the transformer secondary 2, or else with a terminal of the said secondary. 1n the drawing the terminals 37 and -59 are connected to opposite. tcrminals ot' the secondary.

The operation ot accelerating the motor 11- in Fig. 2 is the same in principle as that already described in connection with Fig. 1. To start the motor trom rest, the switch terminals 2-34, 35 and 36 move into the lirst, po-

sition in which they connect with the con- 1 tacts 2-38 and 4-2, 36 engaging with. 38, and 31 and 35 with 42. The result is the connection electrically of the positive terminal 33 with the lowest voltage tap on one side ot the transformer secondary 2 and the positive electrode 31 and $32 to the corresponding tap on the other side of the secondary 2, so that the lowest. voltage impulses attainable are applied to the motor 11. To accelerate the motor 11 t'arther the switch terminals, 3-1, 35. and 36 make contact with the stationary terminals 11, -t2 and 58, res 'iectivcly. The positiveelectrode 33 is then supplied from the same tap as above. The positive. electrode 31 is supplied from the next higher tap from the other side of the secondary 2 and though the positive electrode 32 is connected with the stationary switch terminal 42, it supplies no current, as the positive electrode 31 has a higher voltage. For the is-used for propelling -veh1cles or snmlar service in which no next step, the switch terminals 5H. and iii; are in contact respectively with stationary terminals, 41, 4t) and 38, the result being that the positive electrode 32 is supplied from the second tap on one side of the secondary 2 and the positive electrode 31 from the corresponding tap on the other side of the secondary 2. The positive electrmle 33, though connected to the stationary terminal 38, supplies no current for reasons already explained. By exactly similar steps the voltage applied to the motor 1% is increased step by step until, if desired, the full terminal voltage of the transformer secondary 2 is applied on both sides to the vapor converter 17.

The statements made in the description of Fig. 1, regarding the reduction of speed otthe motor either by proceeding over the steps described in thereverse order or by opening the circuit entirely, apply with equal force to Fig. 2. It is evidently possible, where both sides of a transformer are used to supply all alternations from the source to the motor, that two additional positive electrodes may be used, in which case both sides of the transformer may be stepped up or down at the same time.

The principles described in connection with this invention are applicable to other processes than the acceleration of direct current motors. Any direct current work requiring a variation of potential may make use of this principle and wherever it is convenient and desirable to stop flow of current in a positive electrode by the applica tion of a higher potential either from the same source or other source, this can readily be done by the means of an additional positive terminal above described.

In another application Serial Number 171,882, of which this case is a division, claims are made upon. the method described herein.

I claim as my invention 1. The combination of a direct current work circuit, an alternating current supply,

an hermetically sealed and completely exhausted container, a plurality of electrodes therein, comprising a plurality of anodes and a vaporizable reconstructing cathode therein, means for applying difi'erent voltages from the source upon the anodes and means for supplying direct current from the cathode to the work circuit.-

2. The combination of a direct current work circuit, a vapor converter, alternating current supply obtained from a transformer winding with taps, and means for connecting the vapor converter successively to different taps.

3. The combination of a direct current work circuit, an alternating current supply circuit, a vapor converter having one or more supplementary positive electrodes, and

means for successively connecting non-opcrating positive electrodes to points of higher and higher potential in the supply circuit,

4. In a system of electrical distrilmtion. in which a variable potential direct current circuit is fed from an alternating supply, the combination with direct current translating devices, a vacuum rectifier feeding said electrodes, and suitable sources of potential, said sources of potential providing a plural ity of different electro-motive-forces, of means for applying the several electro-motive-forces successively to the work circuit the point of application being within the said vacuum rectifier and means for returning transmitted impulses.

5. In a system of electrical distribution in which a variable direct current circuit is supplied from an alternating source, the combination with a vacuum rectifier including an exhausted container, a plurality of anodes and a cathode, of a plurality of sources of alternating potential adapted to be successively and simultaneously connected to the said anodes and direct current translating devicesconnected to the cathode, together with means for returning transmitted currents from the said translating devices.

6. In a system of electrical distribution, the combination with a work circuit and a supply of alternating electro motive force provided with a plurality of taps main tained at different potentials, of a vacuum rectifier having a plurality of anodes and a cathode, said rectifier being interposed between the supply and the work circuit, together with means for connecting and disconnecting, successively and sinmltaneously the several taps of the supply to the anodes.

7. The combination of an alternating current supply, a direct current work circuit, a

vacuum rectifier adapted to supply rectified currents from said source to said work circuit, of terminals of said supply adapted to deliver differing potentials, a supplemen tary anode within said rectifier and means for disconnectmg a temporarily non-operating anode and connecting it to a point ofancreased potential in the supply.

8. In a vacuum rectifier including an exhausted container and a negative electrode adapted to supply a direct current work circuit, the combination with a plurality of anodes adapted to receive difl'ierent polarities from a suitable alternating current source, of an additional similar anode, together with means forconnecting temporarily non-operating,anodes successively to points at higher potential of the several polarities and means for disconnecting a nonoperating anode from a point of lower potential.

' 9. The combination with a mercury vapor rectifier having; a plurality of anodes and a suitable cathode, of connections from two anodes to the terminals of a single phase supply. a connection from the cathode to an intermediate point of said supply, and translating devices in said last named connection, together with connectionsbet-ween the third anode and the single phase supply together with means whereby any one of the anodes may be separately disconnected from one point in the supply and connected to another point thereof, alternating on the two terminals of the supply.

10. The combination with a suitable alternating supply and a multiple circuit rectifier, each circuit being supplied with sep arate rectifying means within the rectifier, of suitable connections for simultaneously supplying a plurality of the said lnnltiple paths from points of different potential of the said source and for successively disconnecting individual paths and reconnecting to other points in the supply.

Signed at" New York, in thecounty of New York and State of New York, this 18th day of November, A. D. 1903.

PERCY H. THOMAS.

Witnesses:

WM. H. CAIEL,

GEORGE H. S'roommmcn. 

